Gaze into the sky on a clear, starlit night and feel the fascination
of the cosmic spectacle it offers. Fifty years ago astronomers used
earth-bound telescopes to explore space. The instruments then in
use enabled us to see stars and galaxies so far away that their
light had taken some hundreds of millions of years to reach us.
This year's Nobel Prize in Physics is for another kind of
astronomy, in which the instruments on the COBE satellite were used
to observe radiation that was sent to us about 13 billion years
ago, from another, much earlier era in the development of the universe.

At that time the character of the Universe had just altered. Previously
it had been a dense, hot and impenetrable soup of electrons, protons
and radiation. The temperature was so high and the Universe so dense
that the radiation was swallowed up by the soup, just as light is
veiled by fog. But the Universe is expanding, which means that its
density and the temperature is sinking, and at the same time the
energy of the radiation is lessening – which is the same as
saying its wavelength is rising. The radiation that had previously
been swallowed up by the soup was released – like when the
fog lifts. The temperature had then sunk to 3,000 degrees and it
is estimated that the Universe was about 380,000 years old. The
released radiation could continue its long, unimpeded journey through
the Universe.

During the radiation's 13-billion-year journey the Universe
has expanded mightily and its wavelength has extended one thousandfold,
at the same time the temperature has dropped from 3,000 to about
three degrees above absolute zero. This cold background radiation
fills the Universe and is a relic from its earliest stages, but
it is invisible to the eye. The extended waves can be observed in
the microwave area, with wavelengths of a few millimetres. It is
this original radiation that the COBE satellite observed.

John Mather was responsible for the instruments on board COBE
that were able to determine with great precision the temperature
of the background radiation and also confirm that this spectrum
had the characteristic blackbody form, characterising the hot uniform
state of the early Universe.

George Smoot was in charge of the instruments that were searching
for very small variations – about one per 100,000 – in
the temperature of the background radiation in various directions.
These variations would provide the seeds of the structures, in the
shape of stars and galaxies, that evolved from the original hot,
uniform soup. After collecting data for several years, it was possible
to show that the small variations sought for really existed. The
first step towards understanding the development of structures in
the Universe had been taken.

Dr Mather, Professor Smoot: Cosmology has become a precision science
and your ground-breaking research laid the foundation for that.
With your carefully calibrated instruments you have shown the cosmic
microwave background radiation to follow very precisely a blackbody
form. The in-depth analysis of the radiometer data has shown the
presence of the long sought small temperature anisotropies, the
seed of the structures in the Universe that we observe today. In
your successful experiments you have used space-based instruments
on board the COBE satellite. We are now all together at sea level
in Stockholm, and on behalf of the Royal Swedish Academy of Sciences
it is my privilege and pleasure to congratulate you for your outstanding
work and I now ask you to step forward to receive your Nobel Prizes
from the hands of His Majesty the King.